wtowen

I'm currently running 255/75R17 MTRs on stock rims and thinking about replacing them with the 255/80R17 KM2s in order to gain some extra height. I really like the tall skinny tires. I have been really happy with the MTRs, but would be willing to try the KM2 if it really would give me an extra inch. According to the spec sheets, the KM2 should be exactly 1 inch taller - 32.3 vs 33.3. However, I have heard the KM2's are smaller then advertised, especially when mounted, and the MTRs are more true to size. My MTRs only measure a bit over 31 right now, but there is only about 5/32 tread left, so I assume they were around 32 originally. One post stated the KM2 may only be 32 mounted. If I'm not going to gain any appreciable height I would rather stick with the MTR. Can anyone compare these 2 or at least give me some real life measurements once mounted and on the jeep. Any advice is appreciated. Thanks!

spmitchell86

Someone correct me if I'm wrong but a 1" larger diameter tire would only add 1/2" of height to the rig.

Jonathan_JK

Yep just like going from 35's to 37's only yields 1" extra of ground clearance. Most tires have a listed height on their websites and usually a 35" is actually a 34.8 or less and a 37 is usually a 36.6

Grimmjpr

I ran 255/80/17 KM2s on my 2012 JKR on stock Rubi wheels. I was rather disappointed that they only measured just barely over 32 inches....like 32 1/8 inches tall mounted. I know that tires don't run the same size as stated on the sidewall but BFG specs them at 33.3 so i figured they would have been closer to a 33. i was wrong. If i was to do that again i would go a different route since i didn't gain much over the stock sized tires.

I now run 285/75/17 Toyo ATIIs on my 2015 JKUR stock wheels, and they measure right at a touch over 33 inches tall....it was a good choice without going to a 35.

spmitchell86

So is that why people say not always as tall as advertised? If they're giving the actual height at 33.3" should that be trusted? I'm also looking at these pizza cutters.

Grimmjpr

depending on manufacturer advertised height is based on max psi unloaded i think.....so at street pressure and loaded the height is lower.

Jonathan_JK

Nitto trail grapplers run close to size. I'v seen them on a lot of jeeps and I'm impressed

nthinuf

It is not unusual for people to complain that their tires are an inch or more shorter than they 'thought' they would be.

Your best bet is to find reviews for the specific tires you are looking at to see what actual, measured, sizes people are reporting. Just note that many times people will not measure, and just regurgitate what the specs list, or what they believe the tires to be.

And remember that there will be differences between mfg's for the exact same listed size (KM2's are reported to run a bit short. MTR/K's are reported to run more of an actual, spec'd, size). And running different psi's will change the height. And different rim widths. And vehicle weight. (the same tire, at the same psi, on the same rim, but on a 4door hardtop with full armor and loaded for an expedition vs on a 2door soft top driving off the dealers lot. Exact same tire, very different vehicle weights, different 'measured' tire heights...)

As an example, I ran 325/80/16 Falken Wildpeaks, which is a 37x12.50 equivalent.

Known as: 37" tire
MFG spec: 36.30"
Front tire: 35.50" measured (8.5" rim, 28psi)
Spare tire: 36.60" measured (8.5" rim, might have had 40 psi from the shop, don't remember)

Which number should I use when someone asks how tall they are? I entered 35.5" into the programmer...

wtowen

I expect the measured height of both to be less than spec (although 32 is a bit disappointing for the 255/80 KM2 spec'd at 33.3). I guess i just wonder if both tires lose about the same amount once on the vehicle (i.e. the MTR is measured at a 31 and the KM2 at 32)) or does the MTR lose less and end up being around the same as the nominally bigger KM2 with both around 32. I sure wish I had measured my MTRs when they were new.

Yes, 1 inch diameter is only 1/2 of ground clearance, but every little bit helps. Plus, I'm getting the AEV2.5 and think the 33s will look better, although looks are not the most important factor.

nthinuf

You are probably getting into tire construction now? C/D/E should have different sidewall thickness and varying weights? I would expect a C load to squash easier from vehicle weight than an E, since E's seem to be generally made for heavier duty trucks. And folks on here with E's say they run less psi to soften up the ride, so you could be right back to a height difference from psi.

I think that maybe you are just thinking about it too much. If you want a bigger tire, quit nitpicking and just buy a bigger tire. Look at 34's or 35's instead of 33's.